The epidemiologic study of neurobehavioral effects due to neurotoxicant exposure is necessary in order to understand the possible effects of chemical exposures in occupational and environmental settings. The computer-administered Neurobehavioral Evaluation System (NES) test battery provides a fuller, more standard method of measuring neurobehavioral effects in population groups, compared to the traditional paper and pencil type of clinical neuropsychologicaI tests. However, traditional tests have been validated and thus, have been shown to measure s-f.c.. brain-behavior relationships (Lezak, 1983). The validation process of the NES is ongoing. Studies done to date have not evaluated whether a computerized version of the standard test measures the same level of cognitive functioning, e.g. does pressing a computer key to indicate a positive response to a task presented on the screen involve the same processing 'as verbally responding to a question asked by an examiner? A recent study has been undertaken to evaluate the ability of the NES to detect predicted functional deficits in neurological patients diagnosed with diseases involving cerebral dysfunction, i.e. patients with early Parkinson's disease, multiple sclerosis, and focal strokes. The objective of the proposed study is to validate the use of the NES in patients diagnosed with toxic encephalopathy, i.e. central nervous system (CNS) damage caused by chemical exposure, in order to improve the interpretation of NES test performance in research studies of CNS dysfunction secondary to chemical exposures. Performance on the NES by persons diagnosed with solvent and lead encephalopathy 'will be compared to that of controls to see if the differences reflect a priori brain- behavior relationships. Performance on the NES tests 'will also be compared to performance on the associated standard tests. This study will be important in examining the sensitivity and specificity of the NES to detect subtle brain damage indicative of neurotoxicant exposures. If the NES is shown to be a valid predictor of toxic encephalopathy, it will provide an important research tool in epidemiologic studies of behavioral neurotoxicology and an important clinical tool in the follow-up care of patients with toxic encephalopathy.